Two common RF (radio frequency) spectrum analysis technologies include heterodyne architectures and direct digitization methods. Common as well are various combinations and variants of the two.
Heterodyne architectures work by mixing the input signal with the low-phase noise output of a local oscillator with a known reference frequency, and measuring the power through a high-Q, band-pass filter or high-order low-pass filter. The known reference frequency of the local oscillator is then swept back and forth across the desired frequency space to obtain the power spectral image, one point at a time. The other method, direct digitization, works by employing high-performing, analog-to-digital converters to measure the voltage/current waveform of the signal directly. Fourier analysis and similar mathematical methods are performed by a computer and appropriate digital signal processing software to produce the power spectral image.
A disadvantage of the heterodyne architecture is the need for the local oscillator to sweep across the frequency space, and is limited by the speed at which it can do so while still preserving an accurate measurement across the required frequency space. A disadvantage of a direct digitization method is the tradeoff between the sampling rate and the resolution of analog-to-digital converters, as well as the reliance on secondary software computation, which is in general slower than completely analog methods designed and implemented solely in hardware. In addition, the size and power requirement for both these methods is especially disadvantageous when compared to the invention for higher frequencies.